Ammonia oxidation burners are used in the synthesis of nitric acid. In the ammonia oxidation burner, ammonia (NH3) and oxygen (O2) are catalytically converted to nitric oxide (NO) and water (H2O). The NO obtained is then further used to produce nitric acid.
Platinum-rhodium gauzes, which are placed on a bulk material composed of particles, are ordinary used as catalysts in ammonia oxidation burners. The particles are as a rule composed of a filling material of stoneware, glass, porcelain or stainless steel and are placed in a burner basket arranged inside the burner. The burner basket ordinarily has a gas-permeable bottom plate provided with openings, so that NH3 fed into the burner can flow through the burner basket and the bulk material.
The oxidation of ammonia in the burner requires an operating temperature of approx. 890° C. at a pressure of approx. 10 bar. Because of the high temperature, the burner basket expands during operation of the ammonia oxidation burner. In order to reduce mechanical stresses in the material of the burner basket, the bottom plate and the side wall are often configured as separate components that are arranged in the interior of the ammonia oxidation burner independently of each other. A gas thus forms between the bottom plate and the side wall.
A burner basket of this type, with a bottom plate and a side wall separated from each other by a gap, is described in WO 2013034303 A1. In order to prevent particles of the bulk material from falling out of the basket through the openings in the gas-permeable bottom plate or through the gap between the bottom plate and the side wall, this burner basket is provided with a retaining device in the form of a gas-permeable gauze that covers the gap and the bottom plate. In this burner basket, however, there is a risk that the gauze, as a result of the movements of the bottom plate with respect to the side wall, can detach from the bottom plate and expose the gap or the openings of the bottom plate so that filling material can fall out of the burner basket.